According to Lord Rayleigh, a polar liquid, such as water, becomes unstable e.g. during evaporation in droplet form while levitating, when electrostatic forces between its surface become too great for the droplet's surface tension to oppose. The droplet starts to emit fine jet flows until it reaches stability and the jets form a fine fog, called here the Rayleigh Fog. This disintegration starts immediately when the charge exceeds the surface tension, X approaches unity, as defined by the following formula:X=Q2/[64*Π2*σ*ε0*R3]≦1,where Q=electric charge, Π=3.14 . . . , σ=surface tension, R=droplet radius, ε0 material constant.
In a study published in Science News, Jan. 11, 2003, Vol. 163, page 22, this phenomena was captured by a high speed camera, and the observations indicated that a mother droplet instantly formed about 100 daughter droplets, that collectively carried away less than 0.3% of the mass, and ⅓ of the charge.
This specific behavior pattern is fundamental to all spraying processes, and the associated or introduced electric charge is playing a critical role in creating the often undesired aerosols. A solution for this, in the paper industry common aerosol problem, has been presented in the U.S. Pat. No. 4,944,960 by Donnelly, Kangas and Sundholm, with further disclosure in the European Patent EP 0682571 by the same.
Improvement to the existing nozzle technology for difficult to spray liquids used in the paper industry is shown in the recent U.S. patent application Ser. No. 10/057,583 by Kangas and Diebel.
This invention will further improve the above mentioned spraying technology by enhancing the ability to further disintegrate the liquids and solids, and by stabilizing the spray cone diameter within desired propellant pressure ranges for specific liquids. It include a thermal barrier around the propellant cavity eliminating propellant condensation. In this improved spray apparatus the motive gas is forced to circulate at high speed around the exciting liquid jet. The increase of motive gas pressure will increase the rotation speed, and the physical form of the openings will determine the capacity ranges and spray cone opening. The impact of gas to the sprayed liquid resembles what happens in the center of a tornado, however with the ability to control the forces.
To summarize the benefits in brief:                A high consistency water slurry of paper manufacturing fibers can now for the first time be sprayed directly to form a moving paper web.        The spraying allows a precise layering/engineering of the papers and boards.        The required strength in the end-product can now be tailored according to the need allowing the producer to use the most economical raw materials in this process.        The nozzle allows to complete the new paper manufacturing concept, for which all other key components are already available.        The environmental problems associated with the high water consumption in the paper mills can be lowered considerably.        The other paper making materials, chemicals, fillers and coatings can be sprayed using this same nozzle technology.        This nozzle works also as an efficient chemical reactor and similarly it can be used as an air or oxygen mixer with various fuels.        The spray droplet size with liquids can be controlled from visible to almost instant Rayleigh Fog.        At Rayleigh Fog level, the droplets will provide the largest possible almost instant surface area for chemical reactions for the various processes.        